Rampant Middlesbrough go top of the Championship at the expense of 10-man Derby County.
Ex-Derby loanee Bamford sidefooted in Adam Reach’s cross after six minutes and was brought down by Ryan Shotton for a second-half penalty.
Shotton was dismissed before Leadbitter converted from the spot.
Banned Boro boss Aitor Karanka watched from the stands but it made little difference to the impressive victors.
Derby, leaders at kick-off, were looking for only their second win at the Riverside this century.
But it was the hosts who made the perfect start when Chelsea starlet Bamford tucked away Reach’s pass from seven yards.
It was the promising 21-year-old’s sixth goal in seven games for Middlesbrough, with whom he wants to remain beyond the expiry of his loan deal in January.
Bamford, who would later depart to a standing ovation, came close to doubling the lead after collecting a Leadbitter through ball but was denied by Derby keeper Lee Grant, who completed a superb double save by palming away Jelle Vossen’s rebound effort.
Jeff Hendrick wasted a rare first-half Derby chance, curling tamely at Dimitrios Konstantopoulos after a poor clearance by the Boro keeper.
McClaren made two changes at the break, with Omar Mascarell and Simon Dawkins replaced by Jordan Ibe and Leon Best.
But it failed to stifle the home side’s dominance and the former Middlesbrough boss made his final change on the hour, replacing Hendrick with Will Hughes.
However, moments later things went from bad to worse for Derby when Shotton tripped Bamford in the area and saw red.
The lively Leadbitter thrashed the spot-kick low into Grant’s net to ensure Boro, albeit temporarily, lead the Championship for the first time in two years.